The greatest virtue of Paul Weitz's uneven but amusing satire "American Dreamz" is that it's crammed full of actors doing their damnedest to steal it. This makes the experience of watching the movie sort of like a game of hot potato, as the focus gets grabbed and passed and moved along from one funny performance to another. After a while, you don't quite know where to look.

By the time all the various plotlines converge, the movie's lost its energy. It lacks the sharpness of another recent satire, "Thank You for Smoking," which ticked along so smoothly that the ending took you by surprise — you weren't quite ready to be done with it.

Here, the straight-from-the-headlines plot is full of rich opportunities for satire but ultimately seems a little too tame. If you're going to make a comedy based on the idea of the president being assassinated by a terrorist on live television, you need to be unafraid to be a little nasty.

That said, "American Dreamz" is often a lot of fun, thanks to Weitz's cast.

Hugh Grant plays Martin Tweed, a cad with perfect diction who's host of a TV singing contest that bears a more-than-slight resemblance to "American Idol." (Grant's basically Simon Cowell, just as nasty but with a slightly better fashion sense.) The show's a massive hit, a fact not lost on a troubled White House dealing with an unpopular war in the Middle East, miserable poll numbers and an out-of-touch president (Dennis Quaid, doing a vaguely Texas-style drawl) who doesn't read newspapers.

A Svengali-like chief of staff (Willem Dafoe, looking uncannily like a slightly downsized version of the current vice president) schemes to have his man connect with America by making a guest appearance on Tweed's show. Meanwhile, a bungling terrorist named Omer (Sam Golzari) with dark connections and a love for show tunes finds his way onto the show, as does ambitious small-town songbird Sally Kendoo (Mandy Moore, bright-toothed and strangely tan). There's a bomb, an illicit affair, scenes from a terrorist-training camp, a Carmen Electra cameo and a lot of bad pop music.

So there's plenty to toss around here, though Weitz's screenplay doesn't make all of it stick. Quaid's President Joe Staton, for example, is written as a well-meaning dope, which gives Quaid virtually nothing to play. When Staton finally reads a newspaper, noting, "There's a lot of stuff in here," it falls flat; the character's such a blank slate that the line has no meaning.

Moore's Sally is quickly revealed as a coldhearted schemer, which makes her plotline a bit flat — we know exactly where she's going.

But many of the performances are wickedly good. Shohreh Agdashloo purrs all her lines as a sort of Arab Zsa Zsa Gabor; Tony Yalda, her son and Omer's performance coach, prances through the movie with a brow permanently arched. Chris Klein, as Sally's roadkill boyfriend, taps into the dimwitted, slow-blink charm he first showed in "Election." Judy Greer and John Cho, as Tweed's harried assistants, wouldn't be out of place in a '30s screwball comedy.

And Grant, so at home on the screen as a self-absorbed wretch (shades of Daniel Cleaver in "Bridget Jones's Diary"), brings a sort of languorous grandeur to Tweed. Sick to death of the show he's created, he watches the less-talented contestants with his eyes widening in a mixture of horror and amusement. "That was strange," he tells one, "but rather wonderful."

In this crowded movie, you keep wanting Grant back on the screen; a smug anchor in a crazily free-floating world.